A GUIDE FOR KEEPERS OF POULTRY 201 
of mechanism, admirably adapted to the circumstances 
which are likely to surround it from the time it is ex- 
pelled from the ovary of the hen until the life-germ it 
contains has completed its growth, becomes a complete 
chick and has made its way out of the shell. 
The egg is so constructed that the living germ it con- 
tains is always at the top, no matter how often its posi- 
tion may be changed. This provision of nature gives the 
germ the benefit of the heat of the body of the mother 
when the natural process of incubation is going forward, 
and it follows that the heat of an incubator should be ap- 
plied from the upper side, and the heat from all incu- 
bators is so applied. 
A fertile egg will begin to hatch at somewhere near 90° 
F., but this temperature is not high enough to continue 
the process of incubation, and an egg exposed to this tem- 
perature for some time will merely decay, as the germ 
dies and decays, communicating the elements of decay to 
the other parts of the egg. 
Many otherwise well-informed people think that the 
chick is evolved in some curious way from the contents 
of the shell, but this is not the case. The germ of life 
that exists in a fertile egg bears the same relation to the 
remainder of the contents of the shell that the loaf of 
bread in a baker’s window does to the man who shall 
eat it. When the proper temperature is applied to an 
egg the germ starts into life and begins to grow into a 
chick, consuming the contents of the shell as growth pro- 
ceeds. At the moment of hatching a perfect chick has 
consumed the contents of the shell, except the yolk of the 
egg, which is practically unchanged. The last process of 
incubation is the inclusion of the yolk into the stomach 
of the chick and the closing of the navel through which 
